We have a Universal Distribution Group entry with an email address - we call it udg@example.com.

This item has two members [we call them MemberA and MemberB] which receive in their inbox emails sent to udg@example.com. That far this works perfectly for years.

When for example MemberA wants to reply to an email sent to udg@example.com [which has been delivered into his Inbox] then I have to change the sender address in the From field [udg@example.com is selected from the place displayed as red box]:

enter image description here

Since couple of weeks [I suspect a Microsoft update] I have this very weird behavior:
Very often, too often, the email is rejected by our Exchange with the name of the recipient and that I am not allowed to send on behalf of an other user - but we are not sending it on behalf of!

When we go to the Sent Items folder, press Forward Email, select udg@example.com in the From field then it works!

Here two screenshots how it appears in the Sent Items box:
1) The first try when the email gets rejected. It is in German but you can see it has been sent on behalf of.

enter image description here

And then few seconds later, with exactly the same procedure and same data the email can be sent - you see the on behalf of is missing and therefore it works.

enter image description here

Note: I replaced in the screenshots the real content with samples so it is more understandable.

What confuses me totally is, that mostly the first time the email tries to be sent on behalf of and then few seconds later not.

My question:

What can I do to disable/avoid the on behalf of mechanism?

  • Exchange 2010
  • SBS 2011 Standard
  • Outlook 2013

Replies to comments:

  • A shared mailbox isn't option.
  • Cache mode is disabled.
  • SBS has been restarted several times.
  • For the both users MemberA and MemberB send on behalf is set in the distribution group for udc@example.com.
  • I would appreciate a comment why somebody has down voted this question. What is wrong with it? Missing more information? Bad English? The screenshots? Why the down vote? Give me the chance to improve myself... – Al Bundy May 23 at 10:54

By default Microsoft block the send as for a Distribution Group. Maybe a security update resetted the group's security.

Please validate the security for the account (the distribution group) inside ADUC, not inside Exchange. In the advanced tab inside ADUC you should see the send as security set there for memberA and memberB

If both member manage those email, cna I ask why it's not a shared mailbox ? as often it's best to add the permission to memberA and memberB to manage the shared mailbox.

As such after you can add another account inside their Exchange account. That would open both mailbox inside their outlook.

  • @AlBundy A shared mailbox make it easy to see if an email was replied to, you have the icon that an answer was done, and the sent item is the same between memberA&B, kinda why I suggested that. I have two mailbox inside my iphone for such. For your direct issue I will check then if I see something, as the security is set it's strange. – yagmoth555 May 23 at 13:27
  • You are right regarding the shared mailbox. But, and this is the point, it worked like this for 6! years without any problem. So, as I wrote, I suspect a Microsoft Update which may have changed the behavior and I consider it honestly as a bug. I haven't changed anything --> Since 2-3 weeks I have to send each email twice because the 1st try is sent on behalf of what the Exchange rejects, the 2nd try always works. Even when I set the permission for on behalf of it doesn't change anything. – Al Bundy May 23 at 14:24
  • Pretty sure that there haven't been any updates for Exchange 2010 lately... – Semicolon May 23 at 14:40
  • @AlBundy Can you test by disabling the cache mode in your outlook and retry ? maybe a client problem with it's cache. After that test I would maybe try to add a userC to the DL to make a test, to see if it's not an AD problem. Sometime disabling inheritance on the account and re-enabling it resolve weird right issue. – yagmoth555 May 23 at 14:51
  • What's the mailbox permission ( send on behalf ) of the distribution group? Can OWA send messages properly? You can try to remove the permission and re-add it then verify whether it works. – joyceshen May 24 at 7:28

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